1. Field of the Invention
The present invention relates to a height adjusting device for use in a string pulling block of a stringing machine that may improve the stringing quality and facilitate the height adjustment of the string pulling block.
2. Description of the Prior Arts
Tennis and badminton are both healthy and intellectual sports. To develop the skill of playing tennis or badminton, a racket and strings with a precise pound number are both indispensable winning factors in a tennis or badminton game. Besides, the stringing method of the racket also influences the service lives of the racket and strings.
A prior art stringing machine comprises a base a, a holder b and a string pulling block c (as shown in FIG. 1). The holder b is axially connected to the top of the base a for 360 degree rotation and positioning. The string pulling block c includes a string puller c1 and a lever c2 both arranged thereon. A rod member 10 for combining with the string pulling block c is coupled onto the upper side of the base a (as illustrated in FIG. 2) and includes racks 101 arranged thereon, such that the string pulling block c may move along the racks 101. In other words, the string pulling block c may move relative to the rod member 10.
In operation, the frame d is supported by the holder b, and the string e is fixed between the string puller c1 of the string pulling block c and the frame d (as shown in FIG. 2). Thereafter, the pound number of the string e is set. By rotating the lever c2, the set pound number of the string e is achieved, thereby assembling the longitudinal and lateral strings e of the frame d in turns.
However, such a prior art stringing machine still has the following defects:
1. Easily harming the frame d and the string e: Since the various kinds of frames d are not provided with the same thickness and the heights of the holders b and the string pulling blocks c are fixed, inserting the string e between the string puller c1 of the string pulling block c and the frame d causes an included angle θ therebetween (as illustrated in FIG. 2). Hence, when pulling the string e, the force of the frame d is unequal because of friction, obtaining an imprecise pound number. Furthermore, the string e or the frame d is easily broken because of friction between the through holes formed in the frame d and the string e.
2. Disadvantageous operation: Since the various kinds of frames d are not provided with the same thickness and the heights of the holders b and the string pulling blocks c are fixed, during the rotation of the frame d, a grip d1 of the frame d contacts with the string puller c1 (as illustrated in FIGS. 3 and 4), resulting in an disadvantageous operation.
The present invention has arisen to mitigate and/or obviate the afore-described disadvantages.